The present invention relates to a piezoelectric actuator utilizing a piezoelectric effect and a scanning probe microscope using the same.
In a piezoelectric actuator using a piezoelectric element displaced by applying a voltage, there is known a structure of a laminating type piezoelectric element laminated with a plurality of piezoelectric elements for pressurizing a piezoelectric actuator by using a prepressurizing structure generally using a spring previously in order to prevent an exfoliation among layers of the respective piezoelectric elements or a distortion of a displacement by clearances among the layers to ensure a stable operation (refer to, for example, Patent Reference 1).
However, in a case of driving the piezoelectric actuator at high speed, when a resonance frequency of the spring constituting the prepressurizing structure is low, there is case of jumping up the spring by the piezoelectric element. In this case, the piezoelectric element of the piezoelectric actuator brought into contact with the prepressurizing structure is momentarily separated, during the time period, the piezoelectric element is brought into a state of not being pressurized to pose a problem that not only an operation of the piezoelectric actuator is not stabilized but also a position at which the piezoelectric element and the prepressurizing structure are separated and thereafter brought into contact with each other again is shifted from a position before being separated to change a length of the piezoelectric actuator in a displacing direction.
In order to resolve the problem, it is necessary to be able to follow the high speed operation of the piezoelectric element by using a spring having a high resonance frequency as a prepressurizing structure. As a method of realizing a spring having a high resonance frequency, there is a method of increasing a spring constant by shortening a length of the spring and thickening a thickness thereof, or a method of lightening a mass by using a light material. However, according to the former method, there is a possibility that a prepressure applied on the piezoelectric element is increased by increasing the spring constant and the piezoelectric element cannot be displaced in a case of a small-sized piezoelectric element having a small generating power used for a use of being driven at high speed. In this case, an energy for displacing is changed into a heat amount, and therefore, there is a concern that the piezoelectric element is overheated to be destructed. Further, according to the method of using the light material, generally, a material having a small density is provided with a low Young's modulus, and therefore, an effect cannot be achieved to bring about a drawback that a material is limited.
[Patent Reference 1] JP-A-10-173247
It is a problem of the invention to provide a piezoelectric actuator having a prepressurizing mechanism operated to a piezoelectric element unforcibly and stably even when driven at high speed.
Further, it is a problem of the invention to provide a piezoelectric actuator for detecting a displacement of a piezoelectric element as a large signal and promoting a detection accuracy.
Further, it is a problem of the invention to provide a scanning probe microscope having the above-described effect.